Design of a Laminated Ceramic Composite for Improved Strength and Toughness

Abstract

Adding aluminum titanate to alumina can result in dramatic improvements in toughness and R-curve properties. However, the improved toughness is offset by a significant reduction in strength at small flaw sizes. This problem can be overcome through the use of a laminated composite construction. By placing a thin layer of high-strength material on the surface of a high-toughness body, the toughness and flaw tolerance of the body material can be maintained without sacrificing small flaw strength. In this study, alumina + 20 vol% aluminum titanate (AAT20) was used for both the surface layer and the bulk material. The surface material was a homogeneous, fine-grained mixture of the two phases, while the bulk was an inhomogeneous mixture having a bimodal grain structure. In monolithic form, the homogeneous AAT20 displays a nearly P-'I3 indentation strength response, and the inhomogeneous material displays a flat strength response, indicative of R-curve behavior. The trilayer material shows a composite indentation strength response, with high strength throughout the entire range of starting flaw sizes. A method for predetermining the optimum surface layer thickness is presented. The processing and mechanical properties of these materials will be discussed.

Elaboration and sintering behavior of a laminar ceramic-ceramic material

“…It appears clearly that the experimental data are well aligned. The slope of the straight line should represent the exponent of G in relation (4). A value of 4 is actually found, which must be the case for a grain boundary solid state diffusion mechanism.…”

“…Laminar ceramics appear as a good opportunity to enhance stmctural reliability of materids (I). Structures composed of a stacking of layers of different compositions are actively developed (2)(3)(4)(5). For our part, we are currently working on materials consisting of dense ceramic sheets bonded with porous ceramic layers.…”

Residual Stress on Concentric Laminated Fibrous Al2O3-ZrO2 Composites on Prolonged High Temperature Exposure

“…[4][5][6] Ceramic laminates are considered for structural applications to impart damage tolerance for conditions where cracks extend at constant strains. [7][8][9][10][11][12] Numerous studies have been conducted on the development of different aspects of the contributory effects of the laminated microstructure on Al 2 O 3 -ZrO 2 composites based on different microstructure and design related features. Crack-shielding phenomena related to the presence of the layers(delamination, crack deflection, etc) were studied and documented.…”

Fatiga por contacto esférico en materiales multicapa de alúmina circona

“…Adicionalmente muchas veces estos contactos son cíclicos, con lo que aparecen efectos de fatiga. Con el objeto de mejorar las propiedades de contacto es posible utilizar materiales multicapa donde la capa superficial está a compresión, mejorando la tenacidad superficial aparente [20] y las propiedades tribológicas [21,22].…”